android 向服务器获取数据在界面显示前 android与服务器端数据交互

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网络锐评 2023-06-28 14:42:37

文章标签 android tomcat java ee java 服务端 文章分类 Android 移动开发

本文介绍一下android与服务端的的数据交互

一、搭建一个简易的服务端工程。注备工作：eclipse JavaEE、tomcat的安装。

在eclipse平台创建一个名为MyWeb的Dynamic Web Project,创建名为MyServlet的servlet与android客户端进行数据交互，代码如下：

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


/**
 * Servlet implementation class MyServlet
 */
@WebServlet("/MyServlet")
public class MyServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public MyServlet() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doRequest(request);
        doResponse(response);
    }

    /**
     * 请求的相关处理
     * @param request
     * @throws IOException
     */
    protected void doRequest(HttpServletRequest request) throws IOException{
        //获取请求头携带的参数并打印在控制台
        String token = request.getHeader("token");
        System.out.println("token="+token);

        //获取请求携带的参数并打印
        String name = request.getParameter("name");
        String age = request.getParameter("age");
        System.out.println("name="+name);
        System.out.println("age="+age);
    }

    /**
     * 响应的相关处理
     * @param response
     */
    protected void doResponse(HttpServletResponse response) {
        /**
         * 设置response的相关属性
         */
        response.setContentType("text/html;charset=utf-8");
        PrintWriter writer = null;
        try {
            writer = response.getWriter();

            /**
             * 响应请求的字符串
             */
            String returnJson = "来自服务端的字符串";
            /**
             * 写入json
             */
            writer.write(returnJson);
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            writer.flush();
            writer.close();
        }
    }
}

此时将在工程run在tomcat上。并在浏览器输入http://192.168.1.35:8080/MyWeb/MyServlet?name=changj&age=20，此时浏览器会得到服务器响应的“来自服务端的字符串”，eclipse搭建的服务器端会在控制台打印请求携带的参数name=changj,age=20 的请求信息。此时一个简易的服务器搭建完成。

二、 android客户端的编写。将HttpURLConnection封装成一个工具类，代码如下：

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

/**
 * Created by changj on 16/5/31.
 */
public class HttpUtils {

    /**
     * 请求超时时间5000
     */
    private static final int TIMEOUT_IN_MILLIONS = 5000;
    /**
     * 默认访问的头信息token,密钥参数
     */
    public static final String HTTP_HEADER_PARAM = "token";

    /**
     * 请求回调接口
     */
    public interface HttpCallBackListener {
        //请求成功回调
        public void onFinish(String result);
        //请求失败回调
        public void onError(Exception e);
    }


    /**
     * 异步的Get请求
     *
     * @param urlStr 请求url地址
     * @param listener 请求结果回调
     */
    public static void doGetAsyn(final String urlStr, final HashMap<String,String> params, final HttpCallBackListener listener) {
        new Thread() {
            public void run() {
                try {
                    String result = doGet(urlStr,params);
                    if (listener != null) {
                        listener.onFinish(result);
                    }
                } catch (Exception e) {
                    if (listener != null){
                        listener.onError(e);
                    }
                }

            };
        }.start();
    }

    /**
     * 异步的Post请求
     * @param urlStr
     * @param params
     * @param listener
     */
    public static void doPostAsyn(final String urlStr, final HashMap<String,String> params, final HttpCallBackListener listener) {
        new Thread() {
            public void run() {
                try {
                    String result = doPost(urlStr, params);
                    if (listener != null) {
                        listener.onFinish(result);
                    }
                } catch (Exception e) {
                    if (listener != null){
                        listener.onError(e);
                    }
                }

            };
        }.start();

    }

    /**
     * Get请求，获得返回数据
     *
     * @param urlStr
     * @return
     * @throws Exception
     */
    public static String doGet(String urlStr,HashMap<String,String> params) {
        URL url = null;
        HttpURLConnection conn = null;
        InputStream is = null;
        ByteArrayOutputStream baos = null;
        try {
            StringBuilder sb = null;
            if (params != null) {
                //将HashMap<String,String> params转化成name1=value1&name2=value2 的形式
                sb = toRequestString(params);
                }
            // 将url整合成携带参数的url：http://192.168.1.35:8080/MyWeb/MyServlet?name=changj&age=10
            url = new URL(String.format(urlStr+"?%s",sb));
            // 打开和URL之间的连接
            conn = (HttpURLConnection) url.openConnection();
            //设置读取超时、连接超时
            conn.setReadTimeout(TIMEOUT_IN_MILLIONS);
            conn.setConnectTimeout(TIMEOUT_IN_MILLIONS);
            //设置请求方式
            conn.setRequestMethod("GET");
            // 设置通用的请求属性
            conn.setRequestProperty("accept", "*/*");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("content-Type","application/json;charset=UTF-8");
            conn.setRequestProperty(HTTP_HEADER_PARAM,"CHANGJ");
            if (conn.getResponseCode() == 200) {
                //读取服务器返回的数据流
                is = conn.getInputStream();
                baos = new ByteArrayOutputStream();
                int len ;
                byte[] buf = new byte[128];
                while ((len = is.read(buf)) != -1) {
                    baos.write(buf, 0, len);
                }
                baos.flush();
                return baos.toString();
            } else {
                throw new RuntimeException(" responseCode is not 200 ... ");
            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (is != null)
                    is.close();
            } catch (IOException e) {
            }
            try {
                if (baos != null)
                    baos.close();
            } catch (IOException e) {
            }
            conn.disconnect();
        }

        return null ;

    }

    /**
     * 向指定 URL 发送POST方法的请求
     *
     * @param urlStr
     *            发送请求的 URL
     * @param params
     *            请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
     * @return 所代表远程资源的响应结果
     * @throws Exception
     */
    public static String doPost(String urlStr, HashMap<String,String> params) {
        PrintWriter out = null;
        BufferedReader in = null;
        String result = "";
        try {
            URL url = new URL(urlStr);
            // 打开和URL之间的连接
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            //设置请求方式
            conn.setRequestMethod("POST");
            //设置读取超时、连接超时
            conn.setReadTimeout(TIMEOUT_IN_MILLIONS);
            conn.setConnectTimeout(TIMEOUT_IN_MILLIONS);
            // 设置通用的请求属性
            conn.setRequestProperty("accept", "*/*");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            conn.setRequestProperty("charset", "utf-8");
            conn.setRequestProperty(HTTP_HEADER_PARAM,"CHANGJ");
            conn.setUseCaches(false);
            // 发送POST请求必须设置如下两行
            conn.setDoOutput(true);
            conn.setDoInput(true);

            if (params != null) {
                //将HashMap<String,String> params转化成name1=value1&name2=value2 的形式
                StringBuilder sb = toRequestString(params);
                // 获取URLConnection对象对应的输出流
                out = new PrintWriter(conn.getOutputStream());
                // 发送请求参数
                out.print(sb);
                // flush输出流的缓冲
                out.flush();
            }
            // 定义BufferedReader输入流来读取URL的响应
            in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String line;
            while ((line = in.readLine()) != null) {
                result += line;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        // 使用finally块来关闭输出流、输入流
        finally {
            try {
                if (out != null) {
                    out.close();
                }
                if (in != null) {
                    in.close();
                }
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
        return result;
    }

    /**
     * 将map类型转换成name1=value1&name2=value2 的形式
     * @param map
     * @return
     */
    private static StringBuilder toRequestString(HashMap<String,String> map){
        StringBuilder sb = new StringBuilder();
        Iterator it = map.entrySet().iterator();
        while(it.hasNext()){
            Map.Entry entry = (Map.Entry)it.next();
            Object key = entry.getKey();
            Object val = entry.getValue();
            sb.append(key);
            sb.append("=");
            sb.append(val);
            sb.append("&");
        }
        return sb;
    }
}

activity的编写使用（注意：由于请求采用开辟子线程的异步请求，在更改ui时许借助Handler），代码如下：

Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            String s = (String) msg.obj;
            Toast.makeText(getActivity(),s,Toast.LENGTH_SHORT).show();
        }
    };

    private void request(){
        String url = "http://192.168.1.35:8080/HttpServers/test";
        //String url = "http://192.168.1.35:8080/MyWeb/MyServlet";

        HttpUtils.doGetAsyn(url, new HttpUtils.HttpCallBackListener() {
            @Override
            public void onFinish(String result) {
                Log.d("changj",result);
                Message message = new Message();
                message.obj=result;
                handler.sendMessage(message);
            }

            @Override
            public void onError(Exception e) {

            }

        });

大功告成。

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